This invention relates to a heated railway tank car and more particularly to a heated tank car having the heat exchanger assembly provided therein.
Railway tank cars are commonly used to transport liquid commodities that must be heated to enable the material to flow and unload through the bottom or top mounted discharge valve. At the present time, the material is heated by steam which passes through coils positioned on the exterior surface of the car or by coils which are positioned in the interior of the car. Typical of the prior art devices may be found in the following patents: U.S. Pat. No. 2,145,614 discloses internal and external heating coils. U.S. Pat. No. 2,558,648 shows a heating coil secured exteriorly to a lower portion of a tank car. U.S. Pat. No. 2,772,784 describes the use of a cylindrical jacket encompassing the tank car for the purpose of applying heating from hot water flowing through the jacket. U.S. Pat. No. 3,142,108 shows a plurality of pans attached to the bottom portion of a truck trailer tank for supplying heat to the tank. U.S. Pat. No. 3,176,764 describes an integral-coil tank wall section associated with the lower portion of a tank car to transfer heat to the tank car. U.S. Pat. No. 3,228,466 shows an external heating arrangement for a storage tank. U.S. Pat. No. 3,595,307 shows another arrangement of a heating system disposed exteriorly of a tank car. Finally, U.S. Pat. No. 3,685,458 describes a heating assembly secured exteriorly to a bottom portion of a tank car.
It is apparent from the above-identified patents that there are large areas of the cars that are not subject to the heated steam and that the tank saddles and underframes attached to the bottom end of the tank act as large heat sinks which radiate heat out to the air rather than inwardly to the product. A problem also associated with the external and internal coils is that they are substantially horizontally disposed which makes them difficult to drain after the steam has been disconnected thereby causing freezing and corrosion and subsequent failure to the coils.
Still another problem associated with the prior art is that the material at the upper end of the tank is heated at the same time as the material at the bottom of the tank. The material at the upper portion of the tank is heated for longer than is desirable since the material will not begin to flow from the tank until the material around the discharge valve has been sufficiently heated to enable it to flow from the tank. Still another problem associated with the prior art devices is that a "boot" of material is formed in the bottom end of the car. The "boot" forms due to the heat sink effect of the steel attached to the tank at this particular location. The "boot" is the product remaining in the car after the car has been unloaded and the "boot" keeps building or accumulating thereby reducing the effective capacity of the car. At some time, the "boot" must be removed by chipping or other manual removal process.
Therefore, it is a principal object of the invention to provide an improved heated tank car.
A further object of the invention is to provide a heated tank car having a heat exchanger provided in the interior thereof with the heat exchanger being spaced above the bottom of the tank to achieve a more efficient and uniform heating of the material.
A still further object of the invention is to provide a heated tank car which eliminates the heat sink problems normally associated with conventional heated tank cars.
Still another object of the invention is to provide a heat exchanger for a tank car which is sloped towards the middle of the car so that condensate will drain from the heat exchanger thereby reducing corrosion of the heat exchanger.
Still another object of the invention is to provide a heated tank car which prevents the formation of a "boot" at the bottom of the car.
Still another object of the invention is to provide a heated tank car employing an inclined heat exchanger therein to assist the flow of material to the discharge valve of the car.
These and other objects will be apparent to those skilled in the art.